Case Study: Dimensional Deformation Analysis and Solution for C3604BD Brass Material

For the material grade C3604BD with outer diameter ∅79, dimensional deformation was observed during machining. In contrast, production using the outer diameter ∅80 specification was normal. Corresponding analysis was conducted after sampling, and the results are as follows:

1. Defect Images

As shown in the defect images, compared with the OK sample, the NG sample exhibits a deformation issue at the edge.

2. Chemical Composition Analysis

Order Remarks

Copper Alloy Chemical Composition Analysis (ICP) GB/T 5121.27-2008 ICP Spectrometer T300110

Determination of Copper Content in Brass (Titration) YS/T910-2013 Buret Setup B300018

Conclusion: The chemical composition of the NG part complies with the national standard requirements for C3604BD.

3. Physical Property Analysis

Hardness Testing

Hardness measurements were performed on the center cross-section, edge cross-section, and surface of the material.

① OK Part (∅80)

• Vickers Hardness: HV5 GB/T 4340.1-2009 (AOLONG Vickers Hardness Tester T300111)

② NG Part (∅79)

• Vickers Hardness: HV5 GB/T 4340.1-2009 (Automatic Turret Vickers Hardness Tester T300105)

Summary: The overall hardness of the ∅79 specification material is higher than that of the ∅80 specification. Furthermore, the hardness difference between the central cross-section and the outer region is larger (55.7 HV for ∅79 vs. 33.6 HV for ∅80).

4. Metallographic Analysis

∅80 Metallography

Compare the external metallography with the internal metallography

∅79 Metallography

Compare the external metallography with the internal metallography

Summary: Metallographic analysis shows a clear difference in grain size between the inner and outer microstructures of the ∅79 specification material.

5. Root Cause Analysis

Based on the above analysis, the significant difference in internal and external hardness of the ∅79 part is the direct cause of stress deformation during machining.

Manufacturing Process Flow:

Melting -> Extrusion -> Direct Drawing -> Sizing -> Annealing (Red) -> Inspection -> Packaging

Investigating the production line revealed that our company used low-temperature annealing parameters (280°C / 180min) during the annealing process. Insufficient annealing temperature and duration are the root causes leading to the microstructural grain variance between the interior and exterior of the material.

6. Corrective and Preventive Actions

1. Reduce the machining allowance for direct‑drawing process from 1.00 mm to 0.80 mm to reduce material‑surface stress.
2. Review the annealing parameters again, and perform finished‑product annealing under 350 °C, 240 min.